Yukiharu Matsumoto

Novel ring transformation reactions of xanthine derivatives

Abstract The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed.

Reactions of xanthinium N(7)-ylides with olefinic dipolarophiles

The stereo- and regio-chemical aspects of the reactions of xanthinium N(7)-methylides (2) with olefinic dipolarophiles were elucidated. The reactions of ylides (2) with N-phenylmaleimide afforded stereoselective endo adducts, and with acrylates and acrylonitrile afforded stereo- and regio-selective 6-endo adducts. On the other hand, the reactions of ylides (2) with trans-olefins afforded mixtures of two stereoisomers, the 8-endo-7-exo and 8-exo-7-endo pyrrolo[2,1-f]purine derivatives. Stereochemistry of the adducts was elucidated by 1H n.m.r. and X-ray analysis. The stereoselectivity of the adducts was governed by the balance of steric and electronic effects. The ylides (2) reacted in their Z-form in all reactions investigated. The steric factors of the dipolarophiles were also closely examined.

CYCLOADDITION REACTIONS OF XANTHINIUM N(7)-YLIDES WITH TRANS OLEFINIC DIPOLAROPHILES

Cycloadditions de xanthinyliomethanures-7: obtention de pyrrolo [1,2-f] xanthines; selon les composes de depart, obtention des produits endo et/ou exo